marmalade jars, are also wanted (p. 69). Mustard, buckwheat, or rye make good crops, but many others will do. Leguminous crops, however, show certain abnormal characters, while turnips and cabbages are apt to fail: none of these should be used. It is highly desirable that the pots should be duplicated.

The plots also should be started in the school garden as early as convenient. Eight are required for the set: their treatment is described in Chap. IX. Plots two yards square suffice.

A supply of sand, of clay, and of lime will be wanted, but it is not necessary to have fresh material for each lesson. The sand may be obtained from a builder, a sand pit, the sea shore or from a dealer in chemical apparatus. The clay may be obtained from a brick yard; it gives most satisfactory results after it has been ground ready for brick making. Modelling clay is equally satisfactory. A supply of rain water is desirable.

For a class of twelve children working in pairs at the experiments the following apparatus is wanted for the whole course:—

Six tripods and bunsen burners or spirit lamps [2]
twelve pipe-clay triangles [4]
twelve crucibles or tin lids [3]
sixteen gas jars [4]
twelve beakers 250 c.c. capacity [4]
two beakers 500 c.c.
two beakers 100 c.c.
six egg-cups [2]
twelve funnels [3]
six funnel stands [1]
six perforated glass disks [3]
two tubulated bottles 500 c.c., four corks to fit
cork borers
4 lbs. assorted glass tubing
pestle and mortar
twelve Erlenmeyer flasks 50 c.c. [3]
six saucers
twelve flatbottomed flasks 100 c.c., six fitted with India
rubber stoppers bored with one hole [3], and six
with ordinary corks [3]
box as in Fig. 13
six glass tubes 1/2" diameter, 18" long [2]
six lamp chimneys [3]
six test tubes, corks to fit
three thermometers
soil sampler (p. 88)
balance and weights
two retort stands with rings and clamp.

The figures given in square brackets are the quantities that suffice when the teacher alone does the experiments, it not being convenient for the scholars to do much.

In conclusion the author desires to tender his best thanks to the Rev. Cecil Grant of St George's School, and to Mr W. J. Ashby of the Wye School, for having allowed him the use of their schools and appliances during the progress of these lessons. Especially are his thanks due to Mr Lionel Armstrong for much help ungrudgingly rendered in collecting material, taking photographs, and supervising the experiments.

E. J. R.

HARPENDEN,
February, 1911.

CHAPTER I

WHAT IS THE SOIL MADE OF?

Apparatus required.

Soil and subsoil from a hole dug in the garden. Clay. Six tripods and bunsen burners or spirit lamps [2]. Six crucibles or tin lids and pipe-clay triangles [2]. Twelve glass jars or gas cylinders [4]. Six beakers [2] [1].

If we talk to a farmer or a gardener about soils he will say that there are several kinds of soil; clay soils, gravel soils, peat soils, chalk soils, and so on, and we may discover this for ourselves if we make some rambles in the country and take careful notice of the ground about us, particularly if we can leave the road and walk on the footpaths across the fields. When we find the ground very hard in dry weather and very sticky in wet weather we may be sure we are on a clay soil, and may expect to find brick yards or tile works somewhere near, where the clay is used. If the soil is loose, drying quickly after rain, and if it can be scattered about by the hand like sand on the sea shore, we know we are on a sandy soil and can look for pits where builder's sand is dug. But it may very likely happen that the soil is something in between, and that neither sand pits nor clay pits can be found; if we ask what sort of soil this is we are told it is a loam. A gravel soil will be known at once by its gravel pits, and a chalk soil by the white chalk quarries and old lime kilns, while a peat soil is black, sometimes marshy and nearly always spongey to tread on.

Fig. 1. Soil and subsoil in St George's school garden

We want to learn something of the soil round about us, and we will begin by digging a hole about three feet deep to see what we can discover. At Harpenden this is what the scholars saw:—the top eight inches of soil was dark in colour and easy to dig; the soil below was reddish brown in colour and very hard to dig; one changed into the other so quickly that it was easy to see where the top soil ended and the bottom soil began; no further change could, however, be seen below the eight inch line. A drawing was made to show these things, and is given in Fig. 1. You may find something quite different: sand, chalk, or solid rock may occur below the soil, but you should enter whatever you see into your notebooks and make a drawing, like Fig. 1, to be kept for future use. Before filling in the hole some of the dark coloured top soil, and some of the lighter coloured soil lying below (which is called the subsoil), should be taken for further examination; the two samples should be kept separate and not mixed.

First look carefully at the top soil and rub some of it between your fingers. We found that our sample was wet and therefore contained water; it was very sticky like clay and therefore contained clay; there were a few stones and some grit present and also some tiny pieces of dead plants—roots, stems or leaves, but some so decayed that we could not quite tell what they were. A few pieces of a soft white stone were found that marked on the blackboard like chalk. Lastly, there were a few fragments of coal and cinders, but as these were not a real part of the soil we supposed they had got in by accident. The subsoil was also wet and even more sticky than the top soil, it contained stones and grit, but seemed almost free from plant remains and from the white chalky fragments.

A few experiments will show how much of some of these things are present. The amount of water may be discovered by weighing out ten grams of soil, leaving it to dry in a warm place near the fire or in the sun, and then weighing it again. In one experiment the results were:—

A column 100 millimetres long was drawn to represent the 100 decigrams of soil, and a mark was drawn 17 millimetres up to show the amount of water (see Fig. 2).

Another column should be drawn for the subsoil. On drying the soil it becomes lighter in colour and